The purpose of this study was to produce antisera to the major species of bacteria associated with periodontal disease. These include representative strains of Bacteriodes gingivalis, B. intermedius, Haemophilus actinomycetemcomitans, Eikenella corrodens, Wolinella recta, Fusobacterium nucleatum and Capnocytophaga sp. Indirect fluorescent antibody technique was used to titer rabbit antisera against immunizing strains and also against a battery of oral bacteria to test for cross-reactivity. In general, antisera were specific for representative strains of the immunizing species, while serotypes within a species cross-reacted. F. nucleatum was the only species where a common antigen was not observed among immunizing strains. The antisera produced in this study should prove useful in identifying periodontal bacteria in clinical specimens. Identification can be made without the difficulties of cultural isolation and characterization of these relatively fastidious bacteria.